OpenDNS while very cool, is not the solution to this problem. I have seen this problem occur on several Macs configured with OpenDNS all the way through the router. This 100% a DNS cache corruption issue. When it happens to you, do not restart, do not even quit and relaunch applications. Simply open terminal, execute: sudo dscacheutil -flushcacheThis will completely empty the cache, and I can virtually guarantee that the problem will be immediately resolved, but only temporarily.

Thanks for the awesome info. My mail, all 4 accounts, was doing this ALL the time. I pretty much had enough and was looking for other mail options when I came across this fix. Works perfect, has not timed out since. I was pretty suprised to see there is no place to set timeout limits. But, I don't care now, its fixed!

I struggled with this issue. Changing the DNS did nothing. Flushing the DNS cache did nothing. I finally solved it by loofing in Preferences/Accounts/Advanced where the authentication method had been changed to "Authenticated POP" (APOP). I changed it back to "password" and normal service was resumed.

I have experienced the same problem. I can't tell you WHY it happens, but I can tell you what fixes it (at least for me). Replace the NAME of your incoming mail server with the IP address of your incoming mail server.

If you don't know how to do that, try this. Get the address of your mail server (if you don't know, check your account info in Mail). Launch Network Utility and click on the Lookup Tab. Type in the name of your mail server, and click lookup. Within the info you get back, you'll see your IP address.

Well here's another vote for the cache flush (sudo dscacheutil -flushcache) and in this case, it worked for IMAP accounts rather than POP.

I had 5 IMAP accounts all "offline" and even selecting "take account online" manually, one by one did nothing. Issued the command and started Mail back up and voila, completely resolved. First time I had seen this behavior in Mail.

very frustrating, apple please fix this. i don't know if my problem is exactly the same. i had mail forget my password and flipflop my pop account to Apop. i restored the settings but now it won't connect. it keeps saying stuff about not trusting a security certificate. i click on 'always trust' and 'connect now', but it never works.

I see a lot of posting here about DNS.I have set my own mail up without DNS.I opened Network Utility and pinged my mail servers.It brings up the numeric address for my mail servers.I entered those numbers in the fields for my mail servers.This does not work if you are using a large web-based e-mail provider like gmail since they really don't have a singular server that they use.It works in some scenarios where there is a timed out error message.It suggests to me that the isp DNS server might be overloaded and that by the time it does the lookup and relays the transmission information and the connection is redirected that enough time elapses that an internal clock in the process reaches a threshold and generates a timed out error.

Thanks, Mac, I've never used the Network Utility (the terminal command hadn't helped).

I did as you suggested and pinged them; I have a local ISP. I got different numerics than I was using so I entered the new ones first and then the ones they gave me. I still couldn't connect but found that the SSl Port # had changed. When I reset it, the mail began to work again.

The annoying thing is that the prefs seem to reset themselves frequently and then tells me my selected server is offline. We'll see how long this holds!

I spoke with my ISP this morning and we reset all my mail preferences. Hopefully, that will fix the continual 'off-line' response I was getting when trying to send mail.

They said the Ping result I got yesterday from my use of Network Utility gave me the address of the server I pinged but not the DNS address they want me to use in my System Preference Network DNS settings.

It's working fine again. I'll wait to see if any 'mysterious' changes take place in the prefs.

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